<p>给你一个字符串 <code>s</code>，模拟每秒钟的事件 <code>i</code>：</p>

<ul>
	<li>如果 <code>s[i] == 'E'</code>，表示有一位顾客进入候诊室并占用一把椅子。</li>
	<li>如果 <code>s[i] == 'L'</code>，表示有一位顾客离开候诊室，从而释放一把椅子。</li>
</ul>

<p>返回保证每位进入候诊室的顾客都能有椅子坐的<strong> 最少 </strong>椅子数，假设候诊室最初是 <strong>空的 </strong>。</p>

<p>&nbsp;</p>

<p><strong class="example">示例 1：</strong></p>

<div class="example-block">
<p><strong>输入：</strong><span class="example-io">s = "EEEEEEE"</span></p>

<p><strong>输出：</strong><span class="example-io">7</span></p>

<p><strong>解释：</strong></p>

<p>每秒后都有一个顾客进入候诊室，没有人离开。因此，至少需要 7 把椅子。</p>
</div>

<p><strong class="example">示例 2：</strong></p>

<div class="example-block">
<p><strong>输入：</strong><span class="example-io">s = "ELELEEL"</span></p>

<p><strong>输出：</strong><span class="example-io">2</span></p>

<p><strong>解释：</strong></p>

<p>假设候诊室里有 2 把椅子。下表显示了每秒钟等候室的状态。</p>
</div>
<table>
	<tbody>
		<tr>
			<th>秒</th>
			<th>事件</th>
			<th>候诊室的人数</th>
			<th>可用的椅子数</th>
		</tr>
		<tr>
			<td>0</td>
			<td>Enter</td>
			<td>1</td>
			<td>1</td>
		</tr>
		<tr>
			<td>1</td>
			<td>Leave</td>
			<td>0</td>
			<td>2</td>
		</tr>
		<tr>
			<td>2</td>
			<td>Enter</td>
			<td>1</td>
			<td>1</td>
		</tr>
		<tr>
			<td>3</td>
			<td>Leave</td>
			<td>0</td>
			<td>2</td>
		</tr>
		<tr>
			<td>4</td>
			<td>Enter</td>
			<td>1</td>
			<td>1</td>
		</tr>
		<tr>
			<td>5</td>
			<td>Enter</td>
			<td>2</td>
			<td>0</td>
		</tr>
		<tr>
			<td>6</td>
			<td>Leave</td>
			<td>1</td>
			<td>1</td>
		</tr>
	</tbody>
</table>


<p><strong class="example">示例 3：</strong></p>

<div class="example-block">
<p><strong>输入：</strong><span class="example-io">s = "ELEELEELLL"</span></p>

<p><strong>输出：</strong><span class="example-io">3</span></p>

<p><strong>解释：</strong></p>

<p>假设候诊室里有 3 把椅子。下表显示了每秒钟等候室的状态。</p>
</div>
<table>
	<tbody>
		<tr>
			<th>秒</th>
			<th>事件</th>
			<th>候诊室的人数</th>
			<th>可用的椅子数</th>
		</tr>
		<tr>
			<td>0</td>
			<td>Enter</td>
			<td>1</td>
			<td>2</td>
		</tr>
		<tr>
			<td>1</td>
			<td>Leave</td>
			<td>0</td>
			<td>3</td>
		</tr>
		<tr>
			<td>2</td>
			<td>Enter</td>
			<td>1</td>
			<td>2</td>
		</tr>
		<tr>
			<td>3</td>
			<td>Enter</td>
			<td>2</td>
			<td>1</td>
		</tr>
		<tr>
			<td>4</td>
			<td>Leave</td>
			<td>1</td>
			<td>2</td>
		</tr>
		<tr>
			<td>5</td>
			<td>Enter</td>
			<td>2</td>
			<td>1</td>
		</tr>
		<tr>
			<td>6</td>
			<td>Enter</td>
			<td>3</td>
			<td>0</td>
		</tr>
		<tr>
			<td>7</td>
			<td>Leave</td>
			<td>2</td>
			<td>1</td>
		</tr>
		<tr>
			<td>8</td>
			<td>Leave</td>
			<td>1</td>
			<td>2</td>
		</tr>
		<tr>
			<td>9</td>
			<td>Leave</td>
			<td>0</td>
			<td>3</td>
		</tr>
	</tbody>
</table>


<p>&nbsp;</p>

<p><strong>提示：</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 50</code></li>
	<li><code>s</code> 仅由字母 <code>'E'</code> 和 <code>'L'</code> 组成。</li>
	<li><code>s</code> 表示一个有效的进出序列。</li>
</ul>
